Donald Trump's job approval ratings have remained at about 40 percent since he assumed the U.S. presidency in January, thanks to apparent fervent support from Republicans who seem to believe he was not responsible for the failed effort to replace the Affordable Care Act.

A new CBS News Poll, conducted from March 25 to 28, shows 40 percent of Americans approve of Trump's performance, generally unchanged from the 39 percent he had in late February and 40 percent earlier that month.

The survey's Republican respondents cited an unpopular health care replacement bill as the reason for the failed attempt, and not the president's handling of one of his key campaign promises.

Forty-nine percent of those surveyed said the Republican replacement bill failed because "it wasn't popular," compared to 41 percent of the Republicans who had the same response. Thirty-percent of Republicans said the measure did not get enough support because "Democrats didn't compromise." Only 14 percent of all the survey's total respondents gave that response.

Forty percent of Americans, including 67 percent of Democrats, believe Russia interfered with the 2016 U.S. presidential election with the intent of helping Trump win. Only 13 percent of Republicans, however, agreed with that assessment.

Russian contacts

Most Democrats and independents believe it is somewhat likely Trump associates had inappropriate contact with Russian government officials. But three-fourths of Republicans don't feel such contact was likely.

While most Americans say the FBI should investigate possible associations between the Trump campaign and Russia, only one-third of Republicans agree.

Most of the Republican respondents believe it is likely Trump's offices were wiretapped during the campaign. Half of independents believe they were, while most Democrats don't.

Republican Congressman and House Speaker Paul Ryan gets high marks from fellow Republicans. Sixty-percent of Republicans approve of Ryan's performance, compared to only 33 percent of Americans.